1.What are the requests of uploaded images?

2.How Many Ways Can I Upload Images?

3.What If It Says "The size of picture should be larger than 30*30px!"?

The reason why this occurs is because the picture you uploaded is smaller than 30px. You should avoid small pictures because the smaller the picture, the little information it carries and the less impossible to identify the right fonts. So a picture which is larger than 100pixel is recommended. If you can not find a larger picture, you can enlarge the picture and upload it.